Much keyboard music from the 16th and early 17th centuries has been preserved as hand-written manuscripts in a number of collections held in English Museums. The most important of these collections is the Fitzwilliam Virginal Book since it has almost 300 pieces. A virginal is a small harpsichord-like instrument which was common at the time in aristocratic homes. Among the many pieces by William Byrd in the collection (and also included in a Byrd collection called "My Ladye Nevells Booke") is a set of variations on "Sellenger's Round" (or Sellinger's Rownde), which in turn is thought to be an Irish folk melody (sometimes called "The Beginning of the World") which had been introduced to England. A round is a dance where the dancers form a circle, and the tune continues to be used by dance troops who perform English folk dances including Morris and Maypole style dancing. The melody has been used by other classical composers including Imogen Holst (daughter of Gustav Holst), and the work "Variations on an Elizabethan Theme" which was jointly composed by Arthur Oldham, Michael Tippett, Lennox Berkeley, Benjamin Britten, Humphrey Searle and William Walton.
On mfiles we have two versions of the melody. This "Virginal" version is the first section of Byrd's set of variations, and it consists of 20 bars in total which are repeated. This can be played on any keyboard instrument and an authentic performance should include appropriate ornamentation. The links on the left hand menu will allow you to download the Sheet Music, or MIDI or MP3 versions of the music. The other version on mfiles is a Folk Dance Arrangement for recorder and keyboard, which consists of 24 bars repeated.
The image below is the first page of the sheet music, and here you can download the full sheet music for Sellenger's Round by Byrd for Virginal in PDF format.